1. Field of the Invention
The invention relates to a camera system for a vehicle and can for example be used in a driver assistance system, respectively a mirror substitution system for vehicles, for example commercial vehicles.
2. Description of the Related Art
Commonly known camera systems for vehicles comprise color image sensors for realistic representation of the surroundings of the vehicle in which the camera system is used. By incident infrared light (in the following referred to as IR-light) on the color image sensor, tampering of the color reproduction is possible and, therefore, a representation of the surroundings out of touch with reality. On the other hand, the usage of IR-light improves image brightness in dark surroundings conditions, for example, at night or during a drive through a tunnel
In order to suppress the disadvantageous effects of IR-light on color reproduction in bright surroundings conditions on the one side and to utilize the positive effects of IR-light in dark surroundings conditions on the other side, IR-filters are, for example, used in image acquisition units. In particular, IR-filters are used which are mechanically pivotable between first and second positions for suppressing the effects of IR-light at daytime in the first position and for utilizing these effects at night in the second position.
However, such movable IR-filters are difficult for the usage in the field of vehicles, due to movable mechanical parts in combination with strong vibrations during the operation of the vehicle. Such pivotable IR-filters are mechanically complex and error-prone.
On the one side, commonly known camera systems comprise additional spotlights emitting visible light. Such additional spotlights may have a disturbing effect on image reproduction and may not be allowable due to legal requirements relating to the mounting position.
On the other side, commonly known camera systems use an additional IR-illumination at darkness for improving image reproduction, which, however, results in the above-mentioned disadvantages of color distortion at daytime.
Normally, IR-illumination in camera systems is provided in a wavelength range of approximately 850-950 nm, which is invisible for the human eye, because the sensitivity of the human eye is approximately in the range of 380-780 nm.